Study Shows Fat Cells Help Repair Muscles

Los Angeles: Scientists have found that cells responsible for producing fat also play a role in muscle repair, says a study.

Scientists from the University of California - San Francisco (UCSF) have discovered that muscle repair requires the action of two types of cells known for causing inflammation and forming fat.

The findings of the study in mice, published in the April 11 issue of Cell, showed that a well-known immune cell called eosinophil carries out the muscle repair in two ways - by clearing out cellular debris from damaged tissue and teaming up with a type of cell to trigger muscle re-growth.

The study, led by Ajay Chawla, an associate professor of medicine at the UCSF Cardiovascular Research Institute, found that after eosinophils move to the site of injury, they collaborate with a kind of progenitor cell - immature cells similar to stem cells - to drive the formation of new muscle fibers.

However, the progenitors, called the fibro/adipogenic cells (FAP), do not spin off muscle cells directly, reports Science Daily. "Without eosinophils you cannot regenerate muscle," Chawla said.

He said that when eosinophils at the site of muscle injury secrete a molecule called IL-4, FAP cells respond by expanding their numbers. But instead of becoming fat cells, they act on the true muscle stem cells to trigger the re-growth of muscle fibers.

"They wake up the cells in muscle that divide and form muscle fibers," he said. Eosinophils comprise only a few percent of immune cells.